Design of wideband and low phase noise LC VCO for wireless communications

Abstract

Recently system demands lots of application standards in single device. But unfortunately each standard uses individual system chain. It wastes of chip size, extra cost and complexity. That is because for example if the device needs four standards, four individual system chains will be required and this will lead us to large size. Because of the large size the extra cost will be needed. And for the each system chain control circuit is needed so, this will make the total chip more complex and more size. To solve these problem multi-standard wireless device are now highly demanded. To realize the multi-standard receiver, wideband or multiband voltage controlled oscillator (VCO) is essential to operate the wireless system. However traditional VCO design techniques are not suitable for wideband or multiband VCO design. By taking the VCO core to operate as wideband switched capacitor array is necessary. But, this structure makes the degradation of phase noise. In the master thesis I focus on to design a wideband and low phase noise VCO. There is a filtering technique to lower the phase noise of the narrowband VCOs. It makes the common mode node as high impedance to prevent the down converting of 2nd order harmonic. But, it has difficulty to apply to the wideband VCO. Because LC resonator operate as narrowband, so to cover the wideband filtering multiple passive inductor is required this is the critical disadvantage to the system. So, this paper recommends active inductor filtering technique. Active inductor doesn’t waste extra area of the chip and shows better phase noise than conventional VCO. Wu folded active inductor structure is chosen for the design. Measurement results shows that the power consumption of this VCO is 5 mW form the 1.2 V power supply, the tuning range is from 3.8 GHz to 5.6 GHz, and the phase noise at 1 MHz from the carrier frequency of 4.28 GHz -119.21 dBc/Hz and FoMA shows 189.5. And the core size is 0.344 $mm^{2}$ size is reduce as portion o...